ISLAM MD RABIUL

Effects of depositional structure of sand particle on liquefaction resistance

Hirofumi TOYOTA

The impact of depositional structures of sand particles on their resistance to liquefaction was investigated in this study. Liquefaction is a critical concern in geotechnical engineering, especially in earthquake-prone regions because it causes significant risks to the infrastructure. Saturated sands lose its strength and stiffness under undrained cyclic loading. The study examines various depositional structures, considering loose packing and particle orientation, to understand their influence on the mechanical behavior of sandy soils. A series of triaxial tests was conducted to determine how sand particle orientation affects liquefaction resistance and shear modulus. The goal is to investigate the relationship between particle orientation and liquefaction resistance, as well as the changes in particle alignment that occur during liquefaction. Toyoura sand specimens with regulated particle orientations were used in this experiment. Bender elements are also used to determine the initial shear modulus and investigate the link between shear modulus and liquefaction resistance. The tests were conducted in three different orientations (0°, 45°, and 90°). Before liquefaction, higher particle orientation angle had greater initial shear modulus G0, even in the same density. In the liquefaction resistance, the same tendency was found: Liquefaction resistance increased with larger orientation angles, with the highest result recorded at 90°. For the undrained triaxial cyclic loading, higher orientation angles are more stable against liquefaction. Reliquefaction strength increased for the 0° and 45° orientations than liquefaction strength, while decreasing for the 90° orientation. The microscopic analysis revealed that the tendency of 0° and 45° soil particles were move towards 90° by the liquefaction, but opposite tendency was seen for the 90° orientation: decreases in its orientation angle and concentration (V.M). This study provides valuable insights into the role of depositional structures in liquefaction resistance, offering guidelines for grounds which have liquefaction history. The findings underscore the importance of depositional characteristics in the ground to mitigate liquefaction risks effectively.